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From: Thomas Gleixner <tglx@linutronix.de>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Dmitry Vyukov <dvyukov@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	x86@kernel.org, Alexander Potapenko <glider@google.com>,
	"H . J . Lu" <hjl.tools@gmail.com>,
	Andi Kleen <ak@linux.intel.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [RFCv2 00/10] Linear Address Masking enabling
Date: Thu, 12 May 2022 21:31:22 +0200	[thread overview]
Message-ID: <878rr6v985.ffs@tglx> (raw)
In-Reply-To: <20220512165612.gizedzgtpzbi7jbl@black.fi.intel.com>

On Thu, May 12 2022 at 19:56, Kirill A. Shutemov wrote:
> On Thu, May 12, 2022 at 05:42:58PM +0200, Thomas Gleixner wrote:
>> On Wed, May 11 2022 at 08:49, Peter Zijlstra wrote:
>> > On Wed, May 11, 2022 at 05:27:40AM +0300, Kirill A. Shutemov wrote:
>> > So aren't we creating a problem with LAM_U48 where programs relying on
>> > it are of limited sustainability?
>> >
>> > Any such program simply *cannot* run on 5 level pagetables. Why do we
>> > want to do this?
>> 
>> More bits are better :)
>> 
>> Seriously, I agree that restricting it to LAM57, which gives us 6 bits,
>> makes a lot of sense _and_ makes the whole thing way simpler.
>> 
>> So supporting both needs a truly good justification and a real world use
>> case.
>
> I asked the question before[1]. Basically, more bits more better:
>
> 	For HWASAN #bits == detection probability.
> 	For MarkUS #bits == exponential cost reduction

What is MarkUS? It's not really helpful to provide acronyms which are
not decodable.

> I would really like to have only LAM_U57, but IIUC 6 bits is not always
> enough.
>
> Dmitry, could you elaborate?
>
> [1] https://mobile.twitter.com/dvyukov/status/1342019823400837120

I don't know whether he reacts on posting a link to his twitter
account. I've CC'ed him now. Maybe that works better.

Thanks,

        tglx

  reply	other threads:[~2022-05-12 19:31 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-11  2:27 [RFCv2 00/10] Linear Address Masking enabling Kirill A. Shutemov
2022-05-11  2:27 ` [PATCH] x86: Implement Linear Address Masking support Kirill A. Shutemov
2022-05-12 13:01   ` David Laight
2022-05-12 14:07     ` Matthew Wilcox
2022-05-12 15:06       ` Thomas Gleixner
2022-05-12 15:33         ` David Laight
2022-05-12 14:35     ` Peter Zijlstra
2022-05-12 17:00     ` Kirill A. Shutemov
2022-05-11  2:27 ` [RFCv2 01/10] x86/mm: Fix CR3_ADDR_MASK Kirill A. Shutemov
2022-05-11  2:27 ` [RFCv2 02/10] x86: CPUID and CR3/CR4 flags for Linear Address Masking Kirill A. Shutemov
2022-05-11  2:27 ` [RFCv2 03/10] x86: Introduce userspace API to handle per-thread features Kirill A. Shutemov
2022-05-12 12:02   ` Thomas Gleixner
2022-05-12 12:04     ` [PATCH] x86/prctl: Remove pointless task argument Thomas Gleixner
2022-05-13 12:30       ` [tip: x86/cleanups] " tip-bot2 for Thomas Gleixner
2022-05-13 14:09   ` [RFCv2 03/10] x86: Introduce userspace API to handle per-thread features Alexander Potapenko
2022-05-13 17:34     ` Edgecombe, Rick P
2022-05-13 23:09       ` Kirill A. Shutemov
2022-05-13 23:50         ` Edgecombe, Rick P
2022-05-14  8:37           ` Thomas Gleixner
2022-05-14 23:06             ` Edgecombe, Rick P
2022-05-15  9:02               ` Thomas Gleixner
2022-05-15 18:24                 ` Edgecombe, Rick P
2022-05-15 19:38                   ` Thomas Gleixner
2022-05-15 22:01                     ` Edgecombe, Rick P
2022-05-11  2:27 ` [RFCv2 04/10] x86/mm: Introduce X86_THREAD_LAM_U48 and X86_THREAD_LAM_U57 Kirill A. Shutemov
2022-05-11  7:02   ` Peter Zijlstra
2022-05-12 12:24     ` Thomas Gleixner
2022-05-12 14:37       ` Peter Zijlstra
2022-05-11  2:27 ` [RFCv2 05/10] x86/mm: Provide untagged_addr() helper Kirill A. Shutemov
2022-05-11  7:21   ` Peter Zijlstra
2022-05-11  7:45     ` Peter Zijlstra
2022-05-12 13:06   ` Thomas Gleixner
2022-05-12 14:23     ` Peter Zijlstra
2022-05-12 15:16       ` Thomas Gleixner
2022-05-12 23:14         ` Thomas Gleixner
2022-05-13 10:14           ` David Laight
2022-05-11  2:27 ` [RFCv2 06/10] x86/uaccess: Remove tags from the address before checking Kirill A. Shutemov
2022-05-12 13:02   ` David Laight
2022-05-11  2:27 ` [RFCv2 07/10] x86/mm: Handle tagged memory accesses from kernel threads Kirill A. Shutemov
2022-05-11  7:23   ` Peter Zijlstra
2022-05-12 13:30   ` Thomas Gleixner
2022-05-11  2:27 ` [RFCv2 08/10] x86/mm: Make LAM_U48 and mappings above 47-bits mutually exclusive Kirill A. Shutemov
2022-05-12 13:36   ` Thomas Gleixner
2022-05-13 23:22     ` Kirill A. Shutemov
2022-05-14  8:37       ` Thomas Gleixner
2022-05-18  8:43   ` Bharata B Rao
2022-05-18 17:08     ` Kirill A. Shutemov
2022-05-11  2:27 ` [RFCv2 09/10] x86/mm: Add userspace API to enable Linear Address Masking Kirill A. Shutemov
2022-05-11  7:26   ` Peter Zijlstra
2022-05-12 14:46     ` Thomas Gleixner
2022-05-11 14:15   ` H.J. Lu
2022-05-12 14:21     ` Thomas Gleixner
2022-05-11  2:27 ` [RFCv2 10/10] x86: Expose thread features status in /proc/$PID/arch_status Kirill A. Shutemov
2022-05-11  6:49 ` [RFCv2 00/10] Linear Address Masking enabling Peter Zijlstra
2022-05-12 15:42   ` Thomas Gleixner
2022-05-12 16:56     ` Kirill A. Shutemov
2022-05-12 19:31       ` Thomas Gleixner [this message]
2022-05-12 23:21         ` Thomas Gleixner
2022-05-12 17:22   ` Dave Hansen
2022-05-12 19:39     ` Thomas Gleixner
2022-05-12 21:24       ` Thomas Gleixner
2022-05-13 14:43         ` Matthew Wilcox
2022-05-13 22:59         ` Kirill A. Shutemov
2022-05-12 21:51       ` Dave Hansen
2022-05-12 22:10         ` H.J. Lu
2022-05-12 23:35           ` Thomas Gleixner
2022-05-13  0:08             ` H.J. Lu
2022-05-13  0:46               ` Dave Hansen
2022-05-13  1:27                 ` Thomas Gleixner
2022-05-13  3:05                   ` Dave Hansen
2022-05-13  8:28                     ` Thomas Gleixner
2022-05-13 22:48                     ` Kirill A. Shutemov
2022-05-13  9:14                   ` Catalin Marinas
2022-05-13  9:26                     ` Thomas Gleixner
2022-05-13  0:46               ` Thomas Gleixner
2022-05-13 11:07         ` Alexander Potapenko
2022-05-13 11:28           ` David Laight
2022-05-13 12:26             ` Alexander Potapenko
2022-05-13 14:26               ` David Laight
2022-05-13 15:28                 ` Alexander Potapenko
2022-05-13 23:01           ` Kirill A. Shutemov
2022-05-14 10:00             ` Thomas Gleixner

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